Gaming system, a method of gaming and a game controller

ABSTRACT

A gaming system comprising: a game play mechanism operable by a player to input an initiate base game instruction or to input an initiate feature game instruction; and a game controller arranged to: implement a base game in response to receipt of an initiate base game instruction and to implement a feature game triggerable from the base game when the feature game is triggered; implement a feature game in response to receipt of an initiate feature game instruction; and deduct different credit amounts in response to receipt of the initiate base game instruction and the initiate feature game instruction such that expected return to player is the same irrespective of the instruction.

RELATED APPLICATIONS

This application claims priority to both Australian Provisional Patent Application Nos. 2008901143, having a filing date of Mar. 11, 2008, and 2008904501, having a filing date of Aug. 20, 2008, entitled “A Gaming System, A Method of Gaming and A Game Controller,” which is hereby incorporated by reference herein in its entirety.

BACKGROUND OF THE INVENTION

The present invention relates to a gaming system, a method of gaming and a game controller. Current electronic gaming machines allow a player to place a wager or bet, in return for which a play of the game provided by the gaming machine is conducted. Many gaming machines implement a base game and a feature game which is triggered from the base game if one or more trigger conditions are met. Normally, the feature game has some different rules to the base game: for example, a sequence of free base games or a completely different game. A typical trigger condition is the occurrence of a particular symbol combination in the base game. In some games, a player must place an additional, ante bet to be eligible for the feature (or for a particular variant of the feature).

While such gaming machines provide users with enjoyment, a need exists for alternative gaming systems in order to maintain or increase player enjoyment.

BRIEF SUMMARY OF THE INVENTION

In a first aspect, the invention provides a gaming system comprising:

a game play mechanism operable by a player to input an initiate base game instruction or to input an initiate feature game instruction; and

a game controller arranged to:

implement a base game in response to receipt of an initiate base game instruction and to implement a feature game triggerable from the base game when the feature game is triggered;

implement a feature game in response to receipt of an initiate feature game instruction; and

deduct different credit amounts in response to receipt of the initiate base game instruction and the initiate feature game instruction such that expected return to player is the same irrespective of the instruction.

In an embodiment, the game controller is arranged to deduct a different credit amount in response to the initiate feature game instruction by deducting a multiple of the credit amount deducted for an equivalent win entitlement in the base game.

In an embodiment, the game play mechanism is operable by the player to select from two or more different win entitlements.

In an embodiment, a multiplier (E) is derived in accordance with the equation

${E = \frac{Ft}{{Bt} + F}},$

where B=the expected base win per base game, F=the expected feature win, and t=the trigger rate in number of games.

In an embodiment, the feature game comprises a series of free games (n) and the feature game is retriggerable during the feature game and a multiplier (E) is derived in accordance with the equation

${E = \frac{nmt}{t - n + {nm}}},$

where m=a multiplier applied to wins during the feature, and t=the trigger rate in number of games.

In an embodiment, the price (P) of the game in credits when the player enters the initiate feature game instruction is determined in accordance with the formula:

P=(RR/RTP)*NL*BL,

where RR is the ratio of the return from the feature game to the return from the base game; RTP is the average return to player; NL is the number of lines played; and BL is the bet per line.

In an embodiment, the game controller is implemented, at least in part, by a processor executing code stored in a memory of the gaming system.

In an embodiment, the game controller comprises a base game controller and a feature game controller for implementing the base and feature games respectively.

In an embodiment, the game controller comprises a credit controller arranged to determine the credit amounts to be deducted.

In a second aspect, the invention provides a game controller for a gaming system, the game controller arranged to:

implement a base game in response to receipt of an initiate base game instruction and to implement a feature game triggerable from the base game when the feature game is triggered;

implement a feature game in response to receipt of an initiate feature game instruction; and

deduct different credit amounts in response to receipt of the initiate base game instruction and the initiate feature game instruction such that expected return to player is the same irrespective of the instruction.

In an embodiment, the game controller is arranged to deduct a different credit amount in response to the initiate feature game instruction by deducting a multiple of the credit amount deducted for an equivalent win entitlement in the base game.

In an embodiment, a multiplier (E) is derived in accordance with the equation

${E = \frac{Ft}{{Bt} + F}},$

where B=the expected base win per base game, F=the expected feature win, and t=the trigger rate in number of games.

In an embodiment, the feature game comprises a series of free games (n) and the feature game is retriggerable during the feature game and a multiplier (E) is derived in accordance with the equation

${E = \frac{nmt}{t - n + {nm}}},$

where m=a multiplier applied to wins during the feature, and t=the trigger rate in number of games.

In an embodiment, the price (P) of the game in credits when the player enters the initiate feature game instruction is determined in accordance with the formula:

P=(RR/RTP)*NL*BL,

where RR is the ratio of the return from the feature game to the return from the base game; RTP is the average return to player; NL is the number of lines played; and BL is the bet per line.

In an embodiment, the game controller is implemented, at least in part, by a processor executing code stored in a memory.

In an embodiment, the game controller comprises a base game controller and a feature game controller for implementing the base and feature games respectively.

In an embodiment, the game controller comprises a credit controller arranged to determine the credit amounts to be deducted.

In a third aspect, the invention provides a method of gaming comprising:

implementing a base game in response to receipt of an initiate base game instruction and to implement a feature game triggerable from the base game when the feature game is triggered;

implementing a feature game in response to receipt of an initiate feature game instruction; and

deducting different credit amounts in response to receipt of the initiate base game instruction and the initiate feature game instruction such that expected return to player is the same irrespective of the instruction.

In an embodiment, the method comprises deducting a different credit amount in response to the initiate feature game instruction by deducting a multiple of the credit amount deducted for an equivalent win entitlement in the base game.

In an embodiment, a multiplier (E) is derived in accordance with the equation

${E = \frac{Ft}{{Bt} + F}},$

where B=the expected base win per base game, F=the expected feature win, and t=the trigger rate in number of games.

In an embodiment, the feature game comprises a series of free games (n) and the feature game is retriggerable during the feature game and a multiplier (E) is derived in accordance with the equation

${E = \frac{nmt}{t - n + {nm}}},$

where m=a multiplier applied to wins during the feature, and t=the trigger rate in number of games.

In an embodiment, the price (P) of the game in credits when the player enters the initiate feature game instruction is determined in accordance with the formula:

P=(RR/RTP)*NL*BL,

where RR is the ratio of the return from the feature game to the return from the base game; RTP is the average return to player; NL is the number of lines played; and BL is the bet per line.

In a fourth aspect, the invention provides computer program code which when executed implements the above method.

In a fifth aspect, the invention provides a computer readable medium comprising the above program code.

In a sixth aspect, the invention provides a data signal comprising the above program code.

In a seventh aspect, the invention extends to transmitting the program code.

BRIEF DESCRIPTION OF SEVERAL VIEWS OF THE DRAWINGS

An exemplary embodiment of the invention will now be described with reference to the accompanying drawings in which:

FIG. 1 is a block diagram of the core components of a gaming system;

FIG. 2 is a perspective view of a stand alone gaming machine;

FIG. 3 is a block diagram of the functional components of a gaming machine;

FIG. 4 is a schematic diagram of the functional components of a memory;

FIG. 5 is a schematic diagram of a network gaming system;

FIG. 6 is a further block diagram of a gaming system;

FIG. 7 is an exemplary game play mechanism; and

FIG. 8 is a flow chart of an embodiment.

DETAILED DESCRIPTION OF THE INVENTION

Referring to the drawings, there is shown a gaming system having a game controller arranged to allow a player to purchase direct entry into a feature game.

General Construction of Gaming System

The gaming system can take a number of different forms. In a first form, a stand alone gaming machine is provided wherein all or most components required for implementing the game are present in a player operable gaming machine.

In a second form, a distributed architecture is provided wherein some of the components required for implementing the game are present in a player operable gaming machine and some of the components required for implementing the game are located remotely relative to the gaming machine. For example, a “thick client” architecture may be used wherein part of the game is executed on a player operable gaming machine and part of the game is executed remotely, such as by a gaming server; or a “thin client” architecture may be used wherein most of the game is executed remotely such as by a gaming server and a player operable gaming machine is used only to display audible and/or visible gaming information to the player and receive gaming inputs from the player.

However, it will be understood that other arrangements are envisaged. For example, an architecture may be provided wherein a gaming machine is networked to a gaming server and the respective functions of the gaming machine and the gaming server are selectively modifiable. For example, the gaming system may operate in stand alone gaming machine mode, “thick client” mode or “thin client” mode depending on the game being played, operating conditions, and so on. Other variations will be apparent to persons skilled in the art.

Irrespective of the form, the gaming system comprises several core components. At the broadest level, the core components are a player interface 50 and a game controller 60 as illustrated in FIG. 1. The player interface is arranged to enable manual interaction between a player and the gaming system and for this purpose includes the input/output components required for the player to enter instructions and play the game.

Components of the player interface may vary from embodiment to embodiment but will typically include a credit mechanism 52 to enable a player to input credits and receive payouts, one or more displays 54, a game play mechanism 56 comprising one or more input devices that enable a player to input game play instructions (e.g. to place bets), and one or more speakers 58.

The game controller 60 is in data communication with the player interface and typically includes a processor 62 that processes the game play instructions in accordance with game play rules and outputs game play outcomes to the display. Typically, the game play instructions are stored as program code in a memory 64 but can also be hardwired. Herein the term “processor” is used to refer generically to any device that can process game play instructions in accordance with game play rules and may include: a microprocessor, microcontroller, programmable logic device or other computational device, a general purpose computer (e.g. a PC) or a server.

A gaming system in the form of a stand alone gaming machine 10 is illustrated in FIG. 2. The gaming machine 10 includes a console 12 having a display 14 on which are displayed representations of a game 16 that can be played by a player. A mid-trim 20 of the gaming machine 10 houses a bank of buttons 22 for enabling a player to interact with the gaming machine, in particular during game play. The mid-trim 20 also houses a credit input mechanism 24 which in this example includes a coin input chute 24A and a bill collector 24B. Other credit input mechanisms may also be employed, for example, a card reader for reading a smart card, debit card or credit card. A player marketing module (not shown) having a reading device may also be provided for the purpose of reading a player tracking device, for example as part of a loyalty program. The player tracking device may be in the form of a card, flash drive or any other portable storage medium capable of being read by the reading device.

A top box 26 may carry artwork 28, including for example pay tables and details of bonus awards and other information or images relating to the game. Further artwork and/or information may be provided on a front panel 29 of the console 12. A coin tray 30 is mounted beneath the front panel 29 for dispensing cash payouts from the gaming machine 10.

The display 14 shown in FIG. 2 is in the form of a video display unit, particularly a cathode ray tube screen device. Alternatively, the display 14 may be a liquid crystal display, plasma screen, any other suitable video display unit, or the visible portion of an electromechanical device. The top box 26 may also include a display, for example a video display unit, which may be of the same type as the display 14, or of a different type.

FIG. 3 shows a block diagram of operative components of a typical gaming machine which may be the same as or different to the gaming machine of FIG. 2.

The gaming machine 100 includes a game controller 101 having a processor 102. Instructions and data to control operation of the processor 102 are stored in a memory 103, which is in data communication with the processor 102. Typically, the gaming machine 100 will include both volatile and non-volatile memory and more than one of each type of memory, with such memories being collectively represented by the memory 103.

The gaming machine has hardware meters 104 for purposes including ensuring regulatory compliance and monitoring player credit, an input/output (I/O) interface 105 for communicating with peripheral devices of the gaming machine 100. The input/output interface 105 and/or the peripheral devices may be intelligent devices with their own memory for storing associated instructions and data for use with the input/output interface or the peripheral devices. A random number generator module 113 generates random numbers for use by the processor 102. Persons skilled in the art will appreciate that the reference to random numbers includes pseudo-random numbers.

In the example shown in FIG. 3, a player interface 120 includes peripheral devices that communicate with the game controller 101 comprise one or more displays 106, a touch screen and/or buttons 107, a card and/or ticket reader 108, a printer 109, a bill acceptor and/or coin input mechanism 110 and a coin output mechanism 111. Additional hardware may be included as part of the gaming machine 100, or hardware may be omitted as required for the specific implementation. For example, while buttons or touch screens are typically used in gaming machines to allow a player to place a wager and initiate a play of a game any input device that enables the player to input game play instructions may be used. For example, in some gaming machines a mechanical handle is uses to initiate a play of the game.

In addition, the gaming machine 100 may include a communications interface, for example a network card 112. The network card may, for example, send status information, accounting information or other information to a central controller, server or database and receive data or commands from the central controller, server or database.

FIG. 4 shows a block diagram of the main components of an exemplary memory 103. The memory 103 includes RAM 103A, EPROM 103B and a mass storage device 103C. The RAM 103A typically temporarily holds program files for execution by the processor 102 and related data. The EPROM 103B may be a boot ROM device and/or may contain some system or game related code. The mass storage device 103C is typically used to store game programs, the integrity of which may be verified and/or authenticated by the processor 102 using protected code from the EPROM 103B or elsewhere. It is also possible for the operative components of the gaming machine 100 to be distributed, for example input/output devices 106,107,108,109,110,111 to be provided remotely from the game controller 101.

FIG. 5 shows a gaming system 200 in accordance with an alternative embodiment. The gaming system 200 includes a network 201, which for example may be an Ethernet network. Gaming machines 202, shown arranged in three banks 203 of two gaming machines 202 in FIG. 5, are connected to the network 201. The gaming machines 202 provide a player operable interface and may be the same as the gaming machines 10,100 shown in FIGS. 2 and 3, or may have simplified functionality depending on the requirements for implementing game play. While banks 203 of two gaming machines are illustrated in FIG. 5, banks of one, three or more gaming machines are also envisaged.

One or more displays 204 may also be connected to the network 201. For example, the displays 204 may be associated with one or more banks 203 of gaming machines. The displays 204 may be used to display representations associated with game play on the gaming machines 202, and/or used to display other representations, for example promotional or informational material.

In a thick client embodiment, game server 205 implements part of the game played by a player using a gaming machine 202 and the gaming machine 202 implements part of the game. With this embodiment, as both the game server and the gaming device implement part of the game, they collectively provide a game controller. A database management server 206 may manage storage of game programs and associated data for downloading or access by the gaming devices 202 in a database 206A. Typically, if the gaming system enables players to participate in a Jackpot game, a Jackpot server 207 will be provided to perform accounting functions for the Jackpot game. A loyalty program server 212 may also be provided.

In a thin client embodiment, game server 205 implements most or all of the game played by a player using a gaming machine 202 and the gaming machine 202 essentially provides only the player interface. With this embodiment, the game server 205 provides the game controller. The gaming machine will receive player instructions, pass these to the game server which will process them and return game play outcomes to the gaming machine for display. In a thin client embodiment, the gaming machines could be computer terminals, e.g. PCs running software that provides a player interface operable using standard computer input and output components. Other client/server configurations are possible, and further details of a client/server architecture can be found in WO 2006/052213 and PCT/SE2006/000559, the disclosures of which are incorporated herein by reference.

Servers are also typically provided to assist in the administration of the gaming network 200, including for example a gaming floor management server 208, and a licensing server 209 to monitor the use of licenses relating to particular games. An administrator terminal 210 is provided to allow an administrator to run the network 201 and the devices connected to the network.

The gaming system 200 may communicate with other gaming systems, other local networks, for example a corporate network, and/or a wide area network such as the Internet, for example through a firewall 211.

Persons skilled in the art will appreciate that in accordance with known techniques, functionality at the server side of the network may be distributed over a plurality of different computers. For example, elements may be run as a single “engine” on one server or a separate server may be provided. For example, the game server 205 could run a random generator engine. Alternatively, a separate random number generator server could be provided. Further, persons skilled in the art will appreciate that a plurality of game servers could be provided to run different games or a single game server may run a plurality of different games as required by the terminals.

Further Detail of Gaming System

Referring to FIG. 6, in the embodiment, the player operates game play mechanism 56 to specify their win entitlement and whether they want to play the base game or purchase direct entry into a feature game triggerable from the base game at a trigger rate (t). Game play mechanism 56 provides a series of buttons (either physical buttons or depictions of buttons on a touch screen) that allows the player to make the selections. The selections include a first class of selection that specifies the player's win entitlement and a second class that indicates whether that win entitlement will be evaluated in a base game or a feature game and hence whether a initiate base game or initiate feature game instruction will be communicated from the game play mechanism 56 to the game controller 60. Parts of the player's selection may be combined in a single button. For example, a player's indication that they want to play five lines may also provide an initiate base game instruction to the game controller Depending on the embodiment, not all win entitlements available for entering the base game may be available when entering the feature game. For example, direct entries to the feature game may be restricted to the player choosing to play all win lines.

Persons skilled in the art will appreciate that a player's win entitlement will vary from game to game and may or may not be dependent on player selections. In most spinning reel games, it is typical for the player's entitlement to be affected by the amount they wager and selections they make (i.e. the nature of the wager). For example, a player's win entitlement may be based on how many lines they will play in each game—i.e. a minimum of one line up to the maximum number of lines allowed by the game (noting that not all permutations of win lines may be available for selection, for example, 1, 5, 10 and 20 lines may be offered). Such win lines are typically formed by a combination of displayed symbol positions, one from each reel, the symbol positions being located relative to one another such that they form a line.

In many games, the player's win entitlement is not strictly limited to the lines they have selected, for example, “scatter” pays are awarded independently of a players selection of pay lines and are an inherent part of the win entitlement.

Persons skilled in the art, will appreciate that in other embodiments, the player may obtain a win entitlement by selecting a number of reels to play.

Such games are marketed under the trade name “Reel Power” by Aristocrat Leisure Industries Pty Ltd. The selection of the reel means that each displayed symbol of the reel can be substituted for a symbol at one or more designated display positions. In other words, all displayed symbol positions of a selected reel can be used to form symbol combinations with designated, displayed symbol positions of other reels.

In other embodiments a player win entitlement may be affected by purchasing access to particular pay tables—e.g. a first bet amount entitles the player to wins including cherries and a second amount entitles them to wins including plums.

FIG. 7 shows a game play mechanism 56 of an embodiment where the player selects win lines. Six buttons 711,712,721,722,731,732 are available to the player A player has a choice of whether they will bet 1 credit per line 711 or 5 credits per line. The player completes the specification of their win entitlement by selecting one of buttons 721,722,731,732 which correspond respectively to playing 1 line of the base game, playing 9 lines of the base game, playing 1 line of the feature game and playing 9 lines of the feature game. Each button 721,722,731,732 also provides either an initiate base game play instruction 721,722 or an initiate feature game instruction 731,732 to game controller 60. In some embodiments, the options for direct entry into the feature game may be limited, for example only available if the player is playing the maximum base play option, such as the maximum number lines.

Persons skilled in the art will appreciate that typically feature games are triggered occasional or rarely and with a prize offering significant return to the player. Many features require no additional bet. Accordingly, in order that the gaming system provide the same return to players who enter the base game as enter the feature game. This is achieved by deducting credits for direct entry into the feature game at a multiplier of the amount of credits required for an equivalent base game based on the relative return to player provided by the feature game as described in further detail in the accompanying examples. Factors used in determining the multiplier, or ante-bet for entering the feature game directly include the rate at which the feature triggers, whether a multiplier is applied in the feature and whether the feature can be retriggered.

When game controller 60 receives an initiate play instruction, credit controller 624 ensures that the correct amount of credits will be deducted in dependence on whether the game is to be a base or feature game. Usually, the credits are not deducted from the credit enter specified by meter data 643 until the play has been completed and the win(s) from the player are known so that a net adjustment of the credit meter may be made.

Game controller then initiates either base game controller 622 of feature game controller 623 which implement the base or feature games respectively based on base game data 642 or feature game data 641. Both controllers 622,623 employ random number generator 621 to generate game outcomes which are evaluated to determined whether an award of credits is to be made. If the base game triggers a feature game, base game controller 622 passes control to feature game controller 623 to carry out the triggered feature game before returning control to base game controller 622.

The method provided by the embodiment is summarised in FIG. 8. Initially the game controller 60 waits 810 for an initiate play instruction. It determines 820 whether the initiate play instruction is a base game instruction. If it is, a base game is played 840 and it is determined 850 whether a feature game is triggered. If a feature game is triggered, the method involves playing the feature 860 before returning to a waiting 810 state. If a base game is not selected at 820, then the instruction will be a feature game selection 830 and the feature game is played 860 via direct entry.

Persons skilled in the art will also appreciate that the method of the embodiment could be embodied in program code. The program code could be supplied in a number of ways, for example on a computer readable medium, such as a disc or a memory (for example, that could replace part of memory 103) or as a data signal (for example, by downloading it from a server).

The game can be a spinning reel game, a poker game, a pin and ball game, a keno or bingo game, dice game or card game or any other game known in the art. Further the base and feature games can be different.

In the above examples, the player can at any time purchase the feature game. If the feature game is already in play, then the commencement of the purchased feature game commences at the conclusion of the purchased feature game. In an alternative, embodiment one or more rules specify, when the feature game is eligible to be purchased, for example, the initiate play instruction may need to be in respect of a bet amount per line of a certain value.

Example 1

In this example a feature with average pay of 36 times the total bet may be awarded on average once every 100 games thus contributing an average of 36% return to player. In between features the player may play a 54% base with a total bet per game of 25¢. The total return to the player is 54%+36%=90%. Thus, on average between each feature,

the player spends 100×25¢=$25.00 the player wins 100×54%×25¢=$13.50 the player loses 100×(1−54%)×25¢=$11.50

The feature of 36 times the bet is a reward of

feature pay 36×25¢=$9.00

Hence the $11.50 lost in the base game buys back a $9.00 feature, on average. The net loss of $25 bet−$13.40 base win−$9.00 feature win=$2.50 from $25 bet reflects the 90% return to the player.

Instead of playing 100 base games to get the feature, the player may be offered the chance to buy the feature for an appropriate price. In this case a feature of 36 times the normal bet may be offered to the player for 40 times the normal bet, the return is unchanged as 36/40=90%. A 25 line game on a 1 ¢ denomination with a feature of 36× total bet can offer a feature for a cost of 40×25¢=$10.00. That is, the ante bet multiplier, E=(Feature RTP % *100)/RTP %

A general expression for the ante bet E as a multiplier of the normal bet for this bought feature is as follows:

expected base win (per base game in $) B expected feature win (per feature in $) F trigger rate (in number of games) t

$E = \frac{1}{\frac{B}{F} + \frac{1}{t}}$

Note that the feature win will be in addition to any base win in the game from which it is triggered, so that for each t games there will be t base games +1 feature game. The above expression can be re-written as:

$E = \frac{Ft}{{Bt} + F}$

The numerator represents the return that can be expected over the number of trigger games if each game if it is played as a feature game, whereas the denominator represents the return that would normally be expected from that number of games and hence, E represents the ration of increased return.

Persons skilled in the art will appreciate that the above equations can be applied to both units of currency or units of credits.

Example 2 Free Games with Multiplier

In games, where there the feature is a series n of free base games. F=nB and if a multiplier m is applied during the free games, then F=nMB. So that

$E = \frac{nmt}{t + {nm}}$

Example 3 Retriggerable Feature

In some games, the feature is retriggerable, if the trigger occurs during the free games, a retriggerable free game feature with

free games n multiplier m trigger rate t such as Queen Of The Nile (manufactured by Aristocrat) can be bought with an appropriate ante bet E which will immediately commence play of the n free games retriggerable with probability 1/t and with all wins multiplied by multiplier m.

$E = \frac{nmt}{t - n + {nm}}$

Persons skilled in the art will appreciate that, it is possible to have multiple features such that the feature F₁, bought with bet E₁ may be part of the underlying game or may not. Further features F₂, F₃, F₄, . . . may be created such that F₂ occasionally triggered with ante bet E₁ upon buying F₁, but F₂ may be bought by a further ante bet E₂ etc.

Example 4

The feature game is usually triggered by the occurrence of an event. The event can be a game event (e.g. a certain set of symbols on a pay line), a machine event (e.g. a random number is selected by the machine), a system event or a player tracking system event.

The feature game usually contributes x % to the total return to player. The feature game has a probability of occurrence of p (where 0≦p≦1)

In a spinning reel game with a free game feature, the free game feature normally commences when 3 scattered cats appear anywhere in the window. The free game feature consists of 10 free games playing the lines and bet per line which were in play when the feature was triggered. The feature game returns on average 15 times the bet which was in play when the feature was triggered. The total return to player is 90%.

The player is offered the option at any time that the feature game is not already in play, to purchase the feature game feature.

The price of the feature game is calculated as 15/0.9=17 credits (with rounding to the nearest credit) multiplied by the number of lines to be purchased and multiplied by the bet per line—i.e. P=(RR/RTP)*NL*BL, where: P is the price in credits; RM is the ratio of the return from the feature game to the return from the base game; RTP is the average return to player; NL is the number of lines played; and BL is the bet per line.

The player chooses to purchase 20 lines at 2 credits per line, so the cost is 17*2*20=680 credits. The player presses the purchase “feature game” button and the credit meter decrements by 680 credits. The player is advised that a feature game is now in progress and the feature game commences. At the conclusion of the purchased feature game, we expect the player to receive 15*2*20=600 credits. This gives an expected player return of 88.2%.

Example 5

A spinning reel game is provided with 2 types of feature games. Feature game A is a hold and re-spin game, feature game B is as per the feature game in example 4 and can be purchased in the same manner. In this example, either feature game can be purchased at any time provided a feature game is not already in play. The total game has a return to player of 90%.

Feature game A is a game in which the feature usually commences whenever a pair of “wild” symbols occurs on the first 2 reels. The first 2 reels are held and the player pays the originating bet and the remaining reels are spun. Any win is paid and the player pays the originating bet again, the first 2 reels are held and the remaining reels are spun. At the conclusion of the 2 re-spins, the game returns to the usual game. Feature A is expected to return 10 credits for each credit bet at the time the feature commences.

In this game, the player is playing the game and chooses to purchase feature game A. The price for feature game A is 10/0.9=11 credits times the total bet (with rounding to the nearest credit).

The player selects to purchase feature A with 10 lines played at 5 credits per line. The credit meter is decremented by 550 credits and the player is advised that the feature re-spin game is now in play. If necessary, the screen and reel strips change and the player sees the reels spin and a pair of “wild” symbols land on the first 2 reels. Any prize is paid. The player then bets 550 credits again and the first 2 reels are held and the remaining reels are spun. Any prizes are paid. The player then bets 550 credits and the first 2 reels are held and the remaining reels are spun. Any prizes are paid.

It is expected that 10*5*10=500 credits will be paid on each of the 3 spins. The total return to player is 500+500+500 for an investment of 3*550. This is a return to player of 90.9%.

It will be understood to persons skilled in the art of the invention that many modifications may be made without departing from the spirit and scope of the invention. In particular, features of the above embodiments and examples can be employed to form further embodiments.

It is to be understood that, if any prior art publication is referred to herein, such reference does not constitute an admission that the publication forms a part of the common general knowledge in the art.

In the claims which follow and in the preceding description of the invention, except where the context requires otherwise due to express language or necessary implication, the word “comprise” or variations such as “comprises” or “comprising” is used in an inclusive sense, i.e. to specify the presence of the stated features but not to preclude the presence or addition of further features in various embodiments of the invention. 

1. A gaming system comprising: a game play mechanism operable by a player to input an initiate base game instruction or to input an initiate feature game instruction; and a game controller arranged to: implement a base game in response to receipt of an initiate base game instruction and to implement a feature game triggerable from the base game when the feature game is triggered; implement a feature game in response to receipt of an initiate feature game instruction; and deduct different credit amounts in response to receipt of the initiate base game instruction and the initiate feature game instruction such that expected return to player is the same irrespective of the instruction.
 2. A gaming system as claimed in claim 1, wherein the game controller is arranged to deduct a different credit amount in response to the initiate feature game instruction by deducting a multiple of the credit amount deducted for an equivalent win entitlement in the base game.
 3. A gaming system as claimed in claim 2, wherein the game play mechanism is operable by the player to select from two or more different win entitlements.
 4. A gaming system as claimed in claim 2, wherein a multiplier (E) is derived in accordance with the equation ${E = \frac{Ft}{{Bt} + F}},$ where B=the expected base win per base game, F=the expected feature win, and t=the trigger rate in number of games.
 5. A gaming system as claimed in claim 2, wherein the feature game comprises a series of free games (n) and the feature game is retriggerable during the feature game and a multiplier (E) is derived in accordance with the equation ${E = \frac{nmt}{t - n + {nm}}},$ where m=a multiplier applied to wins during the feature, and t=the trigger rate in number of games.
 6. A gaming system as claimed in claim 1, wherein the price (P) of the game in credits when the player enters the initiate feature game instruction is determined in accordance with the formula: P=(RR/RTP)*NL*BL, where RR is the ratio of the return from the feature game to the return from the base game; RTP is the average return to player; NL is the number of lines played; and BL is the bet per line.
 7. A gaming system as claimed in claim 1, wherein the game controller is implemented, at least in part, by a processor executing code stored in a memory of the gaming system.
 8. A gaming system as claimed in claim 1, wherein the game controller comprises a base game controller and a feature game controller for implementing the base and feature games respectively.
 9. A gaming system as claimed in claim 1, wherein the game controller comprises a credit controller arranged to determine the credit amounts to be deducted.
 10. A game controller for a gaming system, the game controller arranged to: implement a base game in response to receipt of an initiate base game instruction and to implement a feature game triggerable from the base game when the feature game is triggered; implement a feature game in response to receipt of an initiate feature game instruction; and deduct different credit amounts in response to receipt of the initiate base game instruction and the initiate feature game instruction such that expected return to player is the same irrespective of the instruction.
 11. A game controller as claimed in claim 10, arranged to deduct a different credit amount in response to the initiate feature game instruction by deducting a multiple of the credit amount deducted for an equivalent win entitlement in the base game.
 12. A game controller as claimed in claim 11, wherein a multiplier (E) is derived in accordance with the equation ${E = \frac{Ft}{{Bt} + F}},$ where B=the expected base win per base game, F=the expected feature win, and t=the trigger rate in number of games.
 13. A game controller as claimed in claim 11, wherein the feature game comprises a series of free games (n) and the feature game is retriggerable during the feature game and a multiplier (E) is derived in accordance with the equation ${E = \frac{nmt}{t - n + {nm}}},$ where m=a multiplier applied to wins during the feature, and t=the trigger rate in number of games.
 14. A game controller as claimed in claim 10, wherein the price (P) of the game in credits when the player enters the initiate feature game instruction is determined in accordance with the formula: P=(RR/RTP)*NL*BL, where RR is the ratio of the return from the feature game to the return from the base game; RTP is the average return to player; NL is the number of lines played; and BL is the bet per line.
 15. A game controller as claimed in claim 10, implemented, at least in part, by a processor executing code stored in a memory.
 16. A game controller as claimed in claim 10, comprising a base game controller and a feature game controller for implementing the base and feature games respectively.
 17. A game controller as claimed in claim 10, comprising a credit controller arranged to determine the credit amounts to be deducted.
 18. A method of gaming comprising: implementing a base game in response to receipt of an initiate base game instruction and to implement a feature game triggerable from the base game when the feature game is triggered; implementing a feature game in response to receipt of an initiate feature game instruction; and deducting different credit amounts in response to receipt of the initiate base game instruction and the initiate feature game instruction such that expected return to player is the same irrespective of the instruction.
 19. A method as claimed in claim 18, comprising deducting a different credit amount in response to the initiate feature game instruction by deducting a multiple of the credit amount deducted for an equivalent win entitlement in the base game.
 20. A method as claimed in claim 19, wherein a multiplier (E) is derived in accordance with the equation ${E = \frac{Ft}{{Bt} + F}},$ where B=the expected base win per base game, F=the expected feature win, and t=the trigger rate in number of games.
 21. A method as claimed in claim 19, wherein the feature game comprises a series of free games (n) and the feature game is retriggerable during the feature game and a multiplier (E) is derived in accordance with the equation ${E = \frac{nmt}{t - n + {nm}}},$ m=a multiplier applied to wins during the feature, and t=the trigger rate in number of games.
 22. A method as claimed in claim 18, wherein the price (P) of the game in credits when the player enters the initiate feature game instruction is determined in accordance with the formula: P=(RR/RTP)*NL*BL, where RR is the ratio of the return from the feature game to the return from the base game; RTP is the average return to player; NL is the number of lines played; and BL is the bet per line.
 23. A method of gaming according to claim 18 and further including a computer program code.
 24. A method of gaming according to claim 23 and further including a computer readable medium comprising said program code.
 25. A method of gaming according to claim 23 and further including a data signal comprising said program code.
 26. A method of gaming according to claim 23 and further including transmitting said program code. 